Principles and methods of rock support for rockburst control

This paper presents the principles of rock support for rockburst control and three rockburst support systems used in deep metal mines.Before the principles of rock support are presented,rock fracture related to strain burst is first discussed with the help of photos taken on site,and the energy sources and transformations during bursting are illustrated through conceptual models.Surface parallel extension fracture usually occurs in the ejected and surrounding rocks in a strain burst event,while the ejected rock in a fault-slip rockburst is often already pre-fractured before the event.There must be excessive release energy available for rock ejection.The excessive release energy comes from both the ejected rock itself and the surrounding rock.To prevent rock ejection in a rockburst,the support system must be able to dissipate the excessive release energy.All support devices in a support system for rockburst control must be able to dissipate energy,be firmly linked,and be compatible in deformability.A support system for rockburst control comprises surface-retaining devices and yield rockbolts as well as yield cablebolts when needed.Laying mesh on the top of shotcrete liner is a good practice to enhance the surfaceretaining capacity of the support system.Energy-absorbing yield rockbolts dissipate energy either by stretching of the bolt shank or by sliding of the inner anchor in the borehole.Mesh,mesh strap and shotcrete are the surface-retaining devices widely used in the current rock support systems.The three types of rock support used for rockburst control at present are soft support system using Split Set bolts,hybrid support system using rebar and two-point anchored yield bolts,and entirely yieldable support system using strong yield bolts.     

Investment risks under uncertain climate change policy

This paper describes results from a model of decision-making under uncertainty using a real options methodology, developed by the International Energy Agency (IEA). The model represents investment decisions in power generation from the perspective of a private company. The investments are subject to uncertain future climate policy, which is treated as an external risk factor over which the company has no control. The aims of this paper are to (i) quantify these regulatory risks in order to improve understanding of how policy uncertainty may affect investment behaviour by private companies and (ii) illustrate the effectiveness of the real options approach as a policy analysis tool. The study analysed firms’ investment options of coal- and gas-fired power plants and carbon capture and storage (CCS) technologies. Policy uncertainty is represented as an exogenous event that creates uncertainty in the carbon price. Our findings indicate that climate policy uncertainty creates a risk premium for power generation investments. In the case of gas- and coal-fired power generation, the risk premium would lead to an increase in electricity prices of 5–10% in order to stimulate investment. In the case of CCS, the risk premium would increase the carbon price required to stimulate investment by 16–37% compared to a situation of perfect certainty. The option to retrofit CCS acts as a hedge against high future carbon prices, and could accelerate investment in coal plant. This paper concludes that to minimise investment risks in low carbon technologies, policy-makers should aim to provide some long-term regulatory certainty.     

CFD study to determine the optimal configuration of aerators in a full-scale waste stabilization pond

Aerated lagoons (ALs) are important variants of the pond wastewater treatment technology that have not received much attention in the literature. The hydraulic behaviour of ALs and especially the Facultative aerated lagoons (FALs) is very complex since the aeration in these systems is designed for oxygen transfer but not necessarily to create complete mixing. In this work, the energy expenditure of the aerators was studied by means of a scenario analysis. 3D CFD models (one phase and multiphase) of a 3 ha FAL in a waste stabilization pond system in Cuenca (Ecuador) were built for different configurations of aerators. The thrust produced by the aerators was modelled by an external momentum source applied as velocity vectors into the pond fluid. The predictions of a single phase model were in satisfactory agreement with experimental results. Subsequently, a scenario analysis assessing several aeration schemes with different numbers of aerators in operation were tested with respect to velocity profiles and residence time distribution (RTD) curves. This analysis showed that the aeration scheme with all 10 aerators switched on produces a similar hydraulic behaviour compared to using only 6 or 8 aerators. The current operational schemes comprise of switching off some aerators during the peak hours of the day and operating all 10 aerators during night. This current practice could be economically replaced by continuously operating 4 or 6 aerators without significantly affecting the overall mixing. Furthermore, a continuous mixing regime minimises the sediment oxygen demand enhancing the oxygen levels in the pond.     

The architectural legacies of Kisho Kurokawa in China

Kisho Kurokawa (1934–2007) was a world-famous Japanese architect who made his impact on urban architecture in Japan and many other countries. His philosophy of symbiosis influenced several generations of designers and social architects in Japan and the world. In his heyday during the mid 1980s, Kurokawa started a twenty-year journey of architectural design and urban planning in China. His designs in China are closely involved with the contemporary architectural history and practice of the country: for example, in importing foreign architectural design, researching the formal design language and the emerging of private development. The authors traced the footprints of Kurokawa in China and investigated the relevant building and urban design cases. This paper reviews Kurokawa's outstanding works in China, tries to reveal the master's trajectory of adapting ‘symbiosis’ and ‘grey’ concepts in different conditions, and fills a gap in the understanding of modern Chinese and Japanese architecture.     

具有4V至150V宽输入电压范围的高效率100mA同步降压型转换器设计要点532

正引言LTC3639降压型DC/DC转换器的4V至150V宽输入电压范围使得汽车、航空电子设备和分布式电源系统能够:·满足大量的瞬态要求·实现多种宽范围输入电源,例如:高电压DC总线和低电压后备电池·设计一种能适应多种输入电源的通用型电源,从而减少库存量并降低设计和制造的成本     

通信及网络元器件：高度灵活的编解码器是电信公司IPTV计划的重中之重

电信公司正全力以赴与有线电视运营商角力，这场竞争将决定今后十年电视、高速因特网以及电话服务的发展蓝图。在通过使用光纤同轴混合有线电视基础设施和专用线路向客户提供三重业务整合（视频、基于线缆调制解调器的数据服务以及语音服务）方面，有线多服务运营商（MSO）已取得了巨大成功。     

Standards for Grid Computing: Global Grid Forum

Formed in 1999, Global Grid Forum (GGF) is an international organization focused on the development of common practices, agreements, and specifications that will promote interoperability and reuse of Grid technologies. To this end, GGF supports a recommendations process modeled after the Internet Standards Process and carried out through working groups. To ensure that the recommendations process operates with understanding about both research directions and end user requirements, GGF also operates a set of research groups. Finally, GGF supports a set of educational and informational activities designed to support and expand the community of Grid developers, researchers, practitioners and end-users.     

Material Selection for Ceramic Gun Tube Liner

The U.S. Army Research Laboratory is investigating the application of ceramics as bore materials in advanced gun systems. The lower mass and improved high temperature performance of ceramics over traditional gun steels could produce new barrels with improved service life and lower weight while enabling the use of new propellants. Several different ceramics have been researched into which material would best survive the interior ballistic conditions for a variety of different caliber systems. The candidate materials are commercially available monolithic ceramics. Alumina, zirconia, three silicon carbide compositions, two silicon nitride compositions, and a SiAlON material were initially selected. A coupled approach of modeling and experimental verification led to the downselection of the silicon nitride and SiAlON materials as the most capable of surviving the interior ballistic conditions and functioning as a barrel liner. This paper describes the tests, presents the results, and discusses the reasons for these selections.